1GB clients and 1GB uplinks

[J_Worth]

Hello everyone,

 

I am currently experiencing some brain fog! My question is that our school network consists of mostly all Gigabit switches, which provide gigabit links to all client devices with gigabit links between switches. Our core also, operates at 1 gigabit.

 

My question is that surely there is some performance issues having all our clients connect to the network at 1Gb. I was thinking, would it be worthwhile making all of the client connections run at 100Mb with the uplinks and core still running at 1Gb.

 

Would this be better with regards ensuring that the uplinks and core are not overloaded by a few machines thrashing the 1Gb connection?

 

I hope the above makes sense.

 

J. Worth.

[FishCustard]

You are quite correct - it's best practice to have the edge links at least 1 'step' below the trunk links. That way, as you say, one person trying to save 30 GB of MP3s to their user area won't clog the link with 1 Gbps of traffic, the maximum they'd be able to hit is 100 Mbps, leaving plenty of bandwidth available for other users.

[FN-GM]

I think you can use QOS to make sure that users don't hog all the bandwidth on the link.

[MatthewL]

Or upgrade your backbone to 10Gb!

[FishCustard]

I think you can use QOS to make sure that users don't hog all the bandwidth on the link.

 

Isn't that for prioritising certain types of traffic/packet sizes (e.g. VoIP traffic, which will be composed of smaller TCP packets), rather than limiting bandwidth? (honestly not sure!)

[CyberNerd]

I would also agree that the core should operate at speeds an order of magnitude above the clients.

I've been berated by others for suggesting this before on this forum so I understand that it is common for schools to install 1GB/s on clients without updating their servers. In my mind it stands to reason that clients should be restricted and I only started to upgrade clients to 1GB/s after I had upgraded the servers to and the main core uplinks.

[m25man]

A problem solved by using trunks or link aggregation.

If you we're to experience a single client utilising an entire gigabit uplink the trunk will kick in.

Regardless, do any of us actually have any file/disk or resource arrays capable of saturating a 1GB uplink?

I can't think of many. Normally my disk I/O bottlenecks before the LAN does?

[Geoff]

One aspect of 'fully blown' QoS is traffic shaping. i.e. you restrict the bandwidth available to some traffic types so you can guarantee a certain level of service to others. This is above and beyond want most standard switches are capable of doing, as they only offer the ability to prioritise traffic. However in a LAN environment this generally isn't a concern (as opposed to a WAN/Internet gateway where it's always a foremost concern) because upgrading the capacity of your core links is (relatively) cheap. So as other have said as you should be looking at having a 10Gbit core if you are insisting on 1Gbit to the desktop. If you baulk at the costs of this, you might want to look at seeing where you actually need 1Gbit to the desktop and prioritising upgrades there first.

[CyberNerd]

Normally my disk I/O bottlenecks before the LAN does?

 

What are you using on your servers, parallel ATA? Modern SAS drives run at 3 or 6 Gbit/s without any network overhead.